Friday, 9 September 2016

Perspectives on sediment supply: views from water, earth and sky...by Katie Whitbread

A team from BGS Scotland has been getting thigh-deep in the Eddleston Water, a tributary of the River Tweed, developing a new monitoring programme to investigate sediment supply and the evolution of the stream following the reintroduction of channel meanders.

The Eddleston Water, like many streams across the UK, has been strongly affected by historic river straightening to protect road and rail infrastructure, and by the effects of agricultural land use in the catchment. In efforts to protect the nearby town of Peebles from river flooding and improve the ecological status of the stream, the Tweed Forum has been working with partners in the Scottish Environment Protection Agency and CBEC Eco Engineering to re-meander the stream and develop a natural flood management (NFM) scheme which has been funded by the Scottish Government.

Alongside the management works, a long-term monitoring system has been established to assess the impact of the NFM and meandering on the rivers’ ecology and hydrology, including the groundwater system, with partners in Dundee and Edinburgh universities working alongside the BGS Groundwater team. Now a team of BGS geologists are utilising both state-of-the-art technology and ingenious shed-built solutions to get to grips with the catchment’s sediment supply system.

UAV pilot Jez Everest, usually to be found on an Icelandic glacier, has been out with the BGS drone capturing high-resolution aerial footage of the re-meandered reaches in the first tranche of a series of monthly monitoring flights to assess channel evolution following the most recent re-meandering work. Footage showing the connecting of the new meanders can be seen in Jez’s video “Re-meandering the Eddleston Water” from the first survey. The footage will be used to construct a sequence of digital elevations models of the channel system which will be analysed to assess how the new channel morphology evolves.

Meanwhile, Chris Thomas and Katie Whitbread have been out wading to empty a prototype integrated sediment sampler constructed (to high specification) from a length of sewer pipe and some funnels. Despite its humble origins, the sampler performed impeccably, yielding several hundred grams of sediment (a months’ worth) captured from the flows’ suspended load. Following the success of the first sampler, two more are under construction for deployment along the stream, and geochemical analyses in conjunction with connectivity modelling will be used to trace the sediment sources to learn more about the geological controls on sediment supply in the catchment.

Team:
Katie Whitbread – Geology Scotland
Chris Thomas – Geology Scotland
Jez Everest – Marine Geology


 Chris Thomas installing the prototype sediment sampler in the Eddleston Water (K Whitbread/BGS/NERC)
Jez and Chris getting ready to fly the first UAV survey at Lakewood on the Eddleston Water. The sediment bars have formed since this section of the stream was re-meandered two years ago, creating a diverse range of riverine habitats (K Whitbread/BGS/NERC).

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